5 alpha reductase

The enzyme 5 alpha reductase is involved in the conversion of testosterone to dihydrotestosterone. It accomplishes this by reducing the 4,5 double bond. Dihydrotestosterone, or DHT, promotes the growth of the prostate and contributes to male pattern baldnes.

5 AR is produced naturally in the human body. It is responsible for the developement of male genitalia and the prostate gland. It is found in adequate amounts everywhere in the body, except muscle tissue, which is primarily testosterone.

In the scalp, if high amounts of 5 AR are found, it will combine with testosterone to create DHT. This results in hair shaft narrowing, producing progressively finer hairs with each new growth cycle. This will eventually lead to hair loss. Even though you may have normal testosterone levels, your levels of 5 AR might be high, or your levels of free testosterone may be. Free testosterone is the unbound form of the hormone that is converted to DHT in the body. The more free testosterone floating around, the more DHT that will be created.

Studies have shown that individuals with hair loss tend to have higher levels of 5 AR in their bodies. Other studies have shown that different people have different sensitivities to the hormone in the scalp.

Prevention is the best option with 5 AR inhibitors. There are prescription drugs, like Finasteride and Avodart, and over-the-counter remedies/herbs like saw palmetto and reishi mushrooms.